Method for sputtering and a device for sputtering

ABSTRACT

An object of the invention is to provide a method for sputtering and a device for sputtering which can make distribution of film&#39;s thickness and coverage distribution improve, in the device for sputtering constituted of at least a substrate, a substrate holder which holds the substrate, a target for forming a thin film on the substrate, a sputtering cathode in which the target is installed, a means for sputtering which makes materials of the target sputter to the substrate, which are such that sputtering is carried out by making the substrate holder rotate and making a sputter cathode unit comprising at least one sputtering cathode moves along an arc over the rotating substrate held on the substrate holder.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates to a method for sputtering and a devicefor sputtering, which is constituted of at least a substrate and atarget for forming a thin film on the substrate, wherein ionized gas issmashed up to the target and atoms and/or molecules going out from thetarget are clung to the substrate to form the thin film thereon.

[0003] 2. Description of the Related Art

[0004] JP, 11-335835, A discloses a sputtering device in that, in orderto improve evenness of film's thickness, a disc-shaped target and asubstrate on which a film is formed are provided so as to face eachother, and the substrate rotates with revolving on the target, whereinthe substrate is rotated so as to differ an area overlapped between thetarget and itself from the last overlapped area. In the sputteringdevice disclosed in this reference, the target is larger than thesubstrate in order to improve evenness of film's thickness on thesubstrate, in the case that concavities and convexities exist on thesubstrate, thickness of the film formed in the concavity is not even, sothat a problem such that a coverage distribution is made worse isarisen.

[0005] JP, 2001-262336, A discloses a sputtering device in that, inorder to ensure evenness of film's thickness over a wide range of alarge-sized substrate, impedance of a second adjustment circuit isadjusted so as to bring direct-current component of a potential of asubstrate holder close to an electrical potential of plasma to form athin film of an insulator. In this device, a specific angle is formedbetween the target and a surface of the substrate holder, and a centerof the target is not identified to a center of the substrate holder. Inthe sputtering device disclosed in this reference, because a distancebetween a surface of the substrate and the target is inhomogeneous, evenif the substrate is revolved and rotated, operation for a potentialdifference between a cathode and the target and/or operation for animpedance of the adjustment circuit must be worked strictly, so that theproblem such that the operation becomes complex is arisen.

[0006] JP, 2002-20864, A discloses a sputtering device wherein asubstrate and a target are located so as to rush the sputtered particlesto the substrate, rotating the substrate, so that a magnetic film withhigh anisotropic rate can be formed uniformly. In the sputtering devicedisclosed in this reference, because materials rushed out from thetarget are restricted by a plate for modifying distribution, it can beachieved to form a thin film on the substrate, but a problem such thatavailability of the target is very inefficient is arisen. Besides, thereis a problem such that the film is thicker in a center portion of thesubstrate because the center portion thereof is a common portion inevery target.

[0007] JP, 2002-20866, A discloses that, in a sputtering device whichsputters to an object by generating magnetic field on a target andapplying electric field to the target, a means for generating magneticfield is located adjacent to the target and comprises a plurality ofmagnets which rotate complexly so as to combine rotation and revolution.In the sputtering device disclosed in this reference, by rotating theplural magnets located at the back of the target complexly to change themagnetic field complexly, but the complex change of the magnetic fieldmakes electrons moving like a cyclone on the target work complexly, sothat the magnetic field and the electric field are not certain, as aresult, an erosion extent on the target becomes evenness, but smashingdirections of atoms from the target are not uniform, and a problem suchthat distribution of film's thickness and coverage distribution of thesubstrate are not uniform is arisen.

SUMMARY OF THE INVENTION

[0008] Due to the above mentioned, an object of the invention is toprovide a method for sputtering and a device for sputtering which canimprove film's thickness distribution and coverage distribution.

[0009] Accordingly, a method for sputtering in this invention comprises,in a device for sputtering constituted of at least a substrate, asubstrate holder for holding the substrate, a target for forming a thinfilm on the substrate, a sputtering cathode in which the target isinstalled, a means for sputtering which sputters a material of thetarget to the substrate, a step for making the substrate rotate and astep for making a sputtering cathode unit comprising at least onesputtering cathode move along an arc over the rotating substrate held onthe substrate holder and sputter. That is to say, a method forsputtering according to the invention has a novelty in making thesubstrate holder rotate and in making the sputtering cathode unit movealong the arc over the substrate on the rotating substrate holder tosputter.

[0010] The sputtering cathode unit moves passes, reciprocates over thesubstrate at least once or a plurality of times.

[0011] Furthermore, a device for sputtering is constituted of at least asubstrate, a substrate holder which holds the substrate, a target forforming a thin film on the substrate and a sputtering cathode in whichthe target is installed, and comprises a means for rotation which makesthe substrate holder holding the substrate rotate, a sputtering cathodeunit comprising at least one sputtering cathode, a means for movementwhich makes the sputtering cathode unit move along an arc of a circleover the rotating substrate held by the substrate holder and a means forsputtering which sputters during the sputtering cathode unit moves overthe rotating substrate by the means for movement. Thus, it can be carryout the above mentioned method for sputtering concretely.

[0012] The a means for movement is preferably constituted of a means fordriving such as an electric motor and an arm portion turned by the meansfor driving, in a front end of which the sputtering cathode unit isprovided.

[0013] It is preferred that the sputtering cathode has a nozzle portionprojecting to the substrate. Besides, preferably the nozzle portion iscylindrical, but a shape of the nozzle portion is especially not limitedin this invention. Concretely speaking, it is preferred that the nozzleportion is a cylindrical shape in which diameters thereof are equal, aconstitution such that the diameters of it are gradually larger to itsend, a constitution such that the diameter of it are gradually smallerto its end, a constitution such that the diameter of it is are graduallysmaller to its middle portion, or a constitution such that the diameterof it is are gradually larger to its middle portion. Furthermore, it ispreferred that the nozzle portion is barrel-shaped so as to bulge in amiddle portion thereof like an arc, bellbottom-shaped, orbellows-shaped. Thus, it is preferred that the most suitable shape ofthe nozzle portion is selected in consideration of sputtered materials,a size of the substrate and so on.

[0014] It is preferred that the means for movement makes the sputteringcathode unit move, pass or reciprocates over the substrate at least onceor a plurality of times. Moreover, it is preferred that a movement speedof the sputtering cathode unit and a rotation speed of the substrate arecontrolled suitably by a control means. The condition such as the numberof times, the speed and so on of movement, passage or reciprocation areselected suitably in consideration of sputtered materials, formingfilm's thickness, a shape of the substrate and so on.

[0015] It is preferred that sputtering cathode units are provided on afront end of a plurality of arms extending from a rotation shaftconstituting the means for movement respectively, and turn with centerat the rotation shaft. Thus, a plurality of sputtering cathode units cansputter to the substrate. Furthermore, it is preferred that thesputtering cathode unit is constituted of a plurality of sputteringcathodes. It is preferred that the same kind of targets are installed inthe sputtering cathodes respectively, or the different kinds of targetsare installed in the sputtering cathodes respectively. In the case thatthe same kind of targets are installed, thickness of the film formedonce can be increased. In the case that the different kinds of targetsare installed, an alloy can be formed once, and further, a mixed thinfilm can be formed.

[0016] A magnet generating a magnetic field is, preferably, provided inthe sputtering cathode.

[0017] Moreover, it is preferred to be provided with a means for apre-sputter which makes the target in the sputtering cathode dischargeelectricity prior to sputtering to the substrate. Thus, because oxides,etc. clung on a surface of the target can be removed, a quality of thefilm formed at main-sputter can be improved.

[0018] The means for pre-sputter is, preferably, provided with a meansfor detection which detects a condition of sputtering and a means foramendment which judges a condition of sputtering according to the resultdetected by the means for detection and adjusts factors in amain-sputter (sputtering to the substrate) such as an applied electricpower, a movement speed of the sputtering cathode unit and/or a rotationspeed of the substrate.

BRIEF DESCRIPTION OF DRAWINGS

[0019] The various features of novelty which characterize the inventionare pointed out with particularity in the claims annexed to and forminga part of this specification. For a better understanding of theinvention, its operating advantages, and specific objects attained byits use, reference should be had to the accompanying drawings anddescriptive matters in which there are illustrated and describedpreferred working modes of the invention.

[0020]FIG. 1 is a diagrammatic illustration of a device for sputteringaccording to the invention;

[0021]FIG. 2 is a schematic representation for illustrating one exampleof arrangement of the sputtering cathode unit in the device forsputtering according to the invention;

[0022]FIG. 3 is a flowchart diagram showing one example of operation ofthe device for sputtering according to the invention;

[0023]FIGS. 4A and 4B are schematic illustrations showing sputteringmethod according to the invention;

[0024]FIG. 5 is a schematic illustration showing a sputtering cathodeprovided with a nozzle portion at a front end of a shield;

[0025]FIGS. 6A, 6B, 6C and 6D are illustrations showing modifications ofthe nozzle portion; and

[0026]FIG. 7 is a schematic illustration showing a working mode in whichthe sputtering cathode unit is constituted of a plurality of sputteringcathodes.

DETAILED DESCRIPTION OF THE PREFERRED WORKING MODE

[0027] Hereinafter, working modes in this invention are explained due todrawings.

[0028] A device for sputtering 1 shown in FIG. 1 has a vacuum chamber 2.The vacuum chamber 2 has sputtering cathode units 3 which are providedwith sputtering cathodes 30 respectively, a substrate holder 4 holding asubstrate 20 and a mechanism for pre-sputter 5 therein.

[0029] In this working mode, as shown in FIG. 2, the sputtering cathodeunits 3 are, respectively, provided on front ends of a plurality of arms6 radially extending from a rotation shaft 9 of an electric motor 8which is operated by a control unit 7. Thus, the arms 6 can be turnedwith center at the rotation shaft 9 in both directions.

[0030] Besides, The substrate holder 4 is connected to a rotation shaft11 of an electric motor 10 which is operated by the control unit 7, sothat the substrate holder 4 rotates by rotation of the electric motor10.

[0031] Note that the rotation shafts 9 and 11 are secured rotatably viaseal mechanisms 12 and 13 in the vacuum chamber 2.

[0032] The vacuum chamber 2 is provided with a vacuum pump 14 operatedby the control unit 7 and a mechanism for supplying gas 15 whichsupplies gas for sputtering (argon gas in this working mode). Besides,in this working mode, the mechanism for supplying gas is constituted ofa gas receiving tank 15 a and an electromagnetic on-off valve 15 boperated by the control unit 7. Note that there is an inert gas such asargon, xenon, or a mixture gas of the inert gas and oxygen or nitrogenas a gas for sputtering.

[0033] Furthermore, the sputtering cathode 30 is constituted of agrounded shield portion 31, a target 33 which is located in the shieldportion 31 and to which electric power is applied, a magnet portion 34located behind of the target 33, and insulation 32 between the shieldportion 31 and the magnet portion 34. Besides, cooling water andelectric power are supplied via the rotation shaft 9 and arms 6 to thesputtering cathodes 30.

[0034] The substrate holder 4 is grounded via the rotation shaft 11.Note that, in this working mode, the ground is an anode in relation toapplying a minus voltage to the target 33, but there is a case that acertain voltage is applied between the substrate holder 4 and the groundside.

[0035] Due to the above mentioned constitution, the device forsputtering 1 according to this invention is operated, for instance, asshown in a flowchart which starts from step 100 in FIG. 3.

[0036] In step 110, a pressure in the vacuum chamber 2 is decreased to1×10⁻⁴ Pa (8×10⁻⁷ Torr) by operation of the vacuum pump 14. Next, instep 120, by operating the electromagnetic on-off valve 15 b, argon gasis introduced until the pressure in the vacuum chamber 2 reaches to1×10⁻¹ Pa (5×10⁻³ Torr). In step 130, which sputtering cathode unit 3(A-F) shown in FIG. 2 should be used is selected. In step 140, theelectric motor 8 is operated to make one of the sputtering cathode units3(A-F) selected in step 130, in which a desired target (for instance, Φ50 mm Ta target) is installed, move to the mechanism for pre-sputter 5.In step 150, pre-sputter is carried out by applying electric power.Thus, oxide and so on clung on the surface of the target can be removed(cleaning). Note that it is preferred that the mechanism for pre-sputter5 is grounded and, set so as to occur the same condition as discharge tothe substrate 20. Besides, specific sensors are located to detect anyconditions of the pre-sputter, it is preferred to carry out a goodsputtering on the substrate by adjusting voltage, concentration of gasand so on.

[0037] Then, in step 160, the electric motor 10 is operated to make thesubstrate (for instance, (Φ200 mm Si substrate) 20 held on the substrateholder 4 rotate with a specific rotation speed, for instance, 10 rpm. Instep 170, the selected sputtering cathode unit 3 or sputtering cathode30 is located near or adjacent to the substrate holder 4, and then, instep 180, electric power (for instance, 100 WDC) is applied, as shown inFIGS. 4A and 4B, the sputtering cathode unit 3 is moved along a surfaceof the substrate on which a thin film is formed and in an arc orbitpassing over the substrate 20 with operating movement speed (0.1 rpm-1rpm) (main-sputtering). It is basically preferred that the sputteringcathode unit 3 moves, passes or reciprocates over the substrate at leastonce or a plurality of times.

[0038] The sputtering cathode unit 3 is stopped in step 190, whether ornot this working is completed is judged in step 200. When the working iscontinued (N), the above mentioned work is repeated by returning to step130. In this case, a desired sputtering cathode unit 3 or the sputteringcathode 30 is selected, and then the working is continued. Besides, whencompletion of the working is judged (Y), going to step 210, the workingis completed by terminating supply of the electric power, dischargingthe argon gas and returning to a normal pressure in the vacuum chamber2.

[0039] Due to the above working, 0.7 μm of the film's thickness wasgained. Besides, the same thickness of an aluminum film can be formeddue to the same process with another Si substrate 20 and Al target 33.As a result, in the Ta film and the Al film, distribution of the film'sthickness was improved from ±4−2% in a prior method to ±0.7−0.2%, thenumber of particles on the substrate was decreased {fraction (1/30)} ascompared with the case in the prior method, and a rate for forming filmbecame ⅔. This is to depend on that the film's thickness becomes even byrotation of the substrate 20 and revolution of the target 33, and itmeans that the coverage distribution is improved.

[0040] The embodiment shown in FIG. 5 is characterized in that a nozzleportion 35 is provided on a front end of the shield 31. Thus, because arate of sputtering particles in a vertical direction can be increased,the distribution of the film's thickness and the coverage distributionare improved more and unnecessary sputtering particles can be clung onan inner surface of the nozzle portion 35, so that cleaning maintenanceof the device can be facilitated.

[0041] FIGS. 6A-6D show modified embodiments of the nozzle portion 35.FIG. 6A shows a nozzle portion 35 a which has a constitution such as toenlarge its diameters gradually to a front end thereof. FIG. 6B shows anozzle portion 35 b which has a constitution such as to reduce thediameters gradually to a front end thereof. FIG. 6C shows a nozzleportion 35 c which has a constitution such as to enlarge the diametersgradually to a middle portion thereof. FIG. 6D shows a nozzle portion 35d which has a constitution such as to reduce the diameters gradually toa middle portion thereof. As other embodiments, but not shown infigures, a shape of the nozzle portion is so that the side surface isbulged, barrel-shaped, bell-bottom-shaped, or a bellows-shaped so as torepeat enlargement and reduction of the diameters as a wave shape in aside surface thereof. They are selected suitably in consideration ofkinds of the targets, features of the substrate, thickness of film'sthickness and so on.

[0042]FIG. 7 shows an embodiment such that the sputtering cathode unit 3comprises a plurality of (in this working mode, three) the sputteringcathodes 30. In this case, when the sputtering cathodes 30 have the samekind of targets 33 respectively, a rate of forming film once can beincreased and the sputtering can be carried out over a wide range, sothat working time can be reduced and the distribution of film'sthickness and the coverage distribution are improved more.

[0043] When the sputtering cathodes 30 have different targets 33respectively, it can be possible to form an alloy or a mixture thin filmonce. Furthermore, by changing sizes of the targets 33 in the sputteringcathode 30, and/or by adjusting electric power supplied to eachsputtering cathode 30, it can be possible to change a rate of alloy anda mixture rate of the mixture thin film easily.

[0044] Moreover, the distribution of film's thickness and the coveragedistribution can be improved furthermore by rotating the sputteringcathode unit 3 itself.

[0045] Regardless of the number of the sputtering cathodes 30, it can bepossible to form an insulated film by that a high frequency power sourcewith an adjustment device is provided in the target side rotation shaft12.

[0046] Furthermore, due to applying DC or high frequency bias to thesubstrate holder 4, bias-etching to the substrate is made possible, sothat a high density of a thin film can be formed.

[0047] In this working mode, however, the argon gas is used as a processgas for forming film, not only an argon gas but also a mixture gas of aninert gas and oxygen or nitrogen can be used.

[0048] A device according to this invention can be installed to not onlya batch device but also a cluster device.

[0049] The above mentioned device for sputtering according to theworking mode of this invention is such that the substrate 20 and thetarget 33 are located horizontally, but a device for sputtering as theother embodiment is constituted so that the substrate 20 and the target33 are located approximately vertically in the same constitution as thedevice for sputtering shown in FIG. 1.

[0050] In the so-called vertical type of device for sputtering 1, whenfilms of Ta and Al are formed in the same condition as the above case,distribution of the film's thickness was improved from ±4−2% in a priormethod to ±0.7−0.2%, the number of particles on the substrate wasdecreased {fraction (1/50)} as compared with the case in the priormethod, and a rate for forming film became ⅔. This is, as mentionedabove, to depend on that a rate of sputtering articles going straight onthe substrate 20 increases, it means that the coverage distribution isimproved.

[0051] As explaining above, according to this invention, to make thesubstrate rotate and the target move along an arc over the substrate,the distribution of film's thickness and the coverage distribution canbe improved.

[0052] Furthermore, by providing the nozzle portion, it is made possibleto improve the distribution of film's thickness and the coveragedistribution and to cling unnecessary sputtering particles to the innersurface of the nozzle portion, so that cleaning maintenance can befacilitated.

What is claimed is:
 1. A method for sputtering by a device forsputtering constituted of at least a substrate, a substrate holder forholding said substrate, a target for forming a thin film on saidsubstrate, a sputtering cathode in which said target is installed, and ameans for sputtering which makes a material of said target sputter tosaid substrate, comprising: a step for making said substrate holderrotate on its axis; and a step for making a sputtering cathode unitcomprising at least one sputtering cathode move along an arc over saidrotating substrate held on said substrate holder and sputter.
 2. Amethod for sputtering according to claim 1, wherein: said sputteringcathode unit moves, passes or reciprocates over said substrate at leastonce or a plurality of times.
 3. A device for sputtering constituted ofat least a substrate, a substrate holder for holding said substrate, atarget for forming a thin film on said substrate, a sputtering cathodein which said target is installed, and a means for sputtering whichmakes a material of said target sputter to said substrate, comprising: ameans for rotation which makes said substrate holder holding saidsubstrate rotate; a sputtering cathode unit comprising at least onesputtering cathode; a means for movement which makes said sputteringcathode unit move along an arc over said rotating substrate held on saidsubstrate holder; and a means for sputtering which sputters during saidsputtering cathode moves over said rotating substrate held on saidsubstrate holder.
 4. A device for sputtering according to claim 3,wherein: a magnet generating magnetic field is provided on saidsputtering cathode.
 5. A device for sputtering according to claim 4,wherein: said sputtering cathode has a nozzle portion projecting to asubstrate side.
 6. A device for sputtering according to claim 5,wherein: said sputtering cathode units are provided on front ends of aplurality of arms extending from a rotation shaft constituting saidmeans for movement and turns with center at said rotation shaft.
 7. Adevice for sputtering according to claim 6, wherein: a means forpre-sputtering which makes said target of said sputtering cathodedischarge prior to sputtering to said substrate.
 8. A device forsputtering according to claim 7, wherein: said sputtering cathode unitmoves, passes or reciprocates over said substrate at least once or aplurality of times.
 9. A device for sputtering according to claim 7,wherein: said targets which are the same kind are provided on aplurality of said sputtering cathodes, respectively.
 10. A device forsputtering according to claim 7, wherein: said targets which aredifferent kinds are provided on a plurality of said sputtering cathodes,respectively.
 11. A device for sputtering according to claim 7, wherein:said sputtering cathode unit is constituted of a plurality of saidsputtering cathodes.
 12. A device for sputtering according to claim 11,wherein: said sputtering cathode units are provided on front ends of aplurality of arms extending from a rotation shaft constituting saidmeans for movement and turns with center at said rotation shaft.
 13. Adevice for sputtering according to claim 12, wherein: a means forpre-sputtering which makes said target of said sputtering cathodedischarge prior to sputtering to said substrate.
 14. A device forsputtering according to claim 13, wherein: said sputtering cathode unitmoves, passes or reciprocates over said substrate at least once or aplurality of times.
 15. A device for sputtering according to claim 14,wherein: said targets which are the same kind are provided on aplurality of said sputtering cathodes, respectively.
 16. A device forsputtering according to claim 14, wherein: said targets which aredifferent kinds are provided on a plurality of said sputtering cathodes,respectively.
 17. A device for sputtering according to claim 4, wherein:said sputtering cathode units are provided on front ends of a pluralityof arms extending from a rotation shaft constituting said means formovement and turns with center at said rotation shaft.
 18. A device forsputtering according to claim 17, wherein: a means for pre-sputteringwhich makes said target of said sputtering cathode discharge prior tosputtering to said substrate.
 19. A device for sputtering according toclaim 18, wherein: said sputtering cathode unit moves, passes orreciprocates over said substrate at least once or a plurality of times.20. A device for sputtering according to claim 19, wherein: said targetswhich are the same kind are provided on a plurality of said sputteringcathodes, respectively.
 21. A device for sputtering according to claim18, wherein: said targets which are different kinds are provided on aplurality of said sputtering cathodes, respectively.
 22. A device forsputtering according to claim 5, wherein: said sputtering cathode unitsare provided on front ends of a plurality of arms extending from arotation shaft constituting said means for movement and turns withcenter at said rotation shaft.
 23. A device for sputtering according toclaim 22, wherein: a means for pre-sputtering which makes said target ofsaid sputtering cathode discharge prior to sputtering to said substrate.24. A device for sputtering according to claim 23, wherein: saidsputtering cathode unit moves, passes or reciprocates over saidsubstrate at least once or a plurality of times.
 25. A device forsputtering according to claim 24, wherein: said targets which are thesame kind are provided on a plurality of said sputtering cathodes,respectively.
 26. A device for sputtering according to claim 24,wherein: said targets which are different kinds are provided on aplurality of said sputtering cathodes, respectively.